Thermal imaging cameras are useful for detecting radiation in the infrared wavelength range and for producing images of the infrared radiation. Filters can be used to limit the wavelengths of infrared radiation to which the thermal imaging camera is exposed.
Absorption spectroscopy is a technique that measures the intensity of a beam of radiation before and after the radiation has interacted with an unknown sample of material to be analyzed. The incident photons in the beam of radiation are absorbed at the particular wavelengths that correspond to the available energy levels present in the material in the sample. For example, an elevated temperature blackbody radiation source can be placed behind a sample to be analyzed, and the wavelength bands at which the blackbody radiation is absorbed, particularly in the infrared region, provides information that can be used to identify the sample of material. Thermal imaging cameras can be used to image the sample in this type of application. However, placing an elevated temperature blackbody behind a potential leak is impractical and often the signal levels without it are so low that detecting a potential leak is illusive.
In the past, ultraviolet leakage detectors have been used for detecting gas leaks. A dye, which has the property of fluorescing in the visible range when it is illuminated at a particular wavelength band in the ultraviolet range, is injected into the gas. When the dye-injected gas leaks and is appropriately illuminated with ultraviolet radiation, the dye visibly fluoresces, thus indicating the location of leaks to an observer. One example where the dye-injected gas has been useful is detection of leaks in an air conditioning line.